The COVID-19 variant that has ravaged India is now spreading in the United States, and some public health experts have warned that it could interfere with the progress weve made toward our return to normalcy.

The variant (B.1.617.2) is being called the Delta variant as part of the World Health Organizations quest to rename coronavirus strains to Greek letters to avoid any stigma toward countries where new variants pop up. The Delta variant was first detected in India in December 2020 . From there, it spread across the globe and became the dominant form of the coronavirus in the United Kingdom. Now it is thought to account for about 6.1% of cases in the United States and up to 18% in some Western and Midwestern states .

Heres what you need to know about the Delta variant:

Whats different about the Delta coronavirus variant?

The Delta variant has some of the mutations that were identified in previous COVID-19 variants of concern. Whats unique about this one is that these mutations that were detected separately in different variants are now occurring together in the same strain.

These mutations could change the way the virus attaches to a cell, make an activation step easier and block some, but not all of, the antibodies that do the most good, explained Benjamin Neuman , chief virologist at Texas A&M Universitys Global Health Research Complex.

That said, its unclear how these mutations might actually impact the behavior of SARS-CoV-2, and the fact that this variant has two mutations does not necessarily mean it will exhibit the behaviors of both, according to Neuman. Much more research is needed to figure out what the mutations do and how they impact infection.

Preliminary reports suggest the Delta variant is more transmissible (up to 40% more than the original form of the coronavirus from 2019). There have also been anecdotal reports that it causes more severe illness and bizarre symptoms like gangrene and hearing loss.

It does appear that the Delta variant has mutations that are associated with increased transmissibility that were seen in other variants as well, and it does appear to be outcompeting other versions of SARS-CoV-2, said Amesh Adalja , a senior scholar at the Johns Hopkins University Center for Health Security and an infectious disease expert. But there is not conclusive evidence on whether it causes more severe illness, Adalja added.

Researchers also initially thought the Alpha variant the new name for the B.1.1.7 variant first discovered in the U.K. could cause more severe disease. That theory was eventually debunked . Its going to take some time to determine whether the Delta variant causes more severe illness, but Adalja does not expect that to be the case.

Are people with COVID-19 immunity protected from the Delta variant?

The Delta variant only seems to be a real issue in people who are unprotected; those whove been fully vaccinated appear to have sufficient protection against this variant. This is likely why the Delta variant became such a problem in India, where the vaccination rate was (and is) low.

People who previously had COVID-19 also appear to similarly be protected. Evidence has found that though antibody levels drop after infection, another part of our immune system the cell-mediated immune response can kick into action. This part attacks the spike protein (which is what antibodies go after) and several other locations on the coronavirus. And thats whats going to keep people with immunity safe, Neuman explained.

A study from Public Health England found that two doses of the Pfizer vaccine were 88% effective against symptomatic disease from the Delta variant (compared with 93% effective against the Alpha variant). Two doses of the AstraZeneca vaccine were 60% effective against symptomatic disease (compared with 66% against the Alpha variant). The biggest takeaway from the study, however, is that you really need the second dose for the highest level of protection from this variant. Both the AstraZeneca and Pfizer vaccines were 33% effective against the Delta variant in people who had only one dose.

Plus, the vaccines are likely even more effective against hospitalization and death which is what most experts are concerned with. Where it matters, to me, is not mild disease. Its severe disease, hospitalization and death and there, all variants basically fall to the vaccines, Adalja said.

Though more research has been conducted on the Pfizer and AstraZeneca vaccines against the Delta variant, all of the vaccines go after the same part of the coronavirus, so they are likely to work the same way, according to Neuman.

Will the Delta variant affect us worse as we head into the fall?

It could, but not in the same way things unfolded in 2020. When the climate gets cooler in the fall and we head indoors together, we will likely see more contagious variants spread among unvaccinated pockets with low natural immunity.

What we probably wont see is hospitals pushed to their limits. Too many high-risk people have been vaccinated, Adalja said, so with the most vulnerable at risk for hospitalization and death protected, its unlikely well see our hospitals in crisis mode again.

The easiest and safest way to eliminate the threat of this (and future) variants is to get the shot. The solution to any variant is to be fully vaccinated, Adalja said.

Experts are still learning about COVID-19. The information in this story is what was known or available as of publication, but guidance can change as scientists discover more about the virus. Please check the Centers for Disease Control and Prevention for the most updated recommendations.